This invention relates, in general, to doping of a semiconductive material, and more particularly, to doping of layers used in a light-emitting device.
Recently, there has been an increased interest in a laser device called a vertical cavity surface emitting laser (VCSEL). Advantages of VCSEL devices are that the device emits light perpendicular to the wafer, providing better potential for the array formation, integration, as well as on-wafer testing. Conventionally, VCSEL devices utilize highly doped aluminum gallium arsenide layers (Al.sub.x Ga.sub.1-x As/Al.sub.y Ga.sub.1-y As) in their Distributed Bragg Reflectors (DBRs). These VCSEL devices generally operate with a range of wavelengths that approximates the visible (0.65 microns) to the infrared (0.98 microns). Thus, DBRs are made to reflect wavelengths longer than 0.57 microns. Typically, DBRs are doped with either a p-type dopant or an n-type dopant. Growth of these layered structures is achieved by epitaxial growth techniques, such as MOCVD (Metal-organic Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy), or CBE (Chemical Beam Epitaxy).
However, selection of an appropriate p-type dopant for fabricating these doped layers is now a problem. For example, while zinc (Zn) is commonly used as a p-type dopant in MOCVD, it possesses a very high diffusion coefficient, thus making it unusable for doping DBRs. Another commonly used p-type dopant source is carbon tetrachloride (CCl.sub.4) for carbon (C), which is a p-type dopant. Unfortunately, carbon tetrachloride is an ozone depleting material that is currently being withdrawn from use, thus making CCl.sub.4 unusable. Since these two commonly used p-type dopants are not usable, it is clear that an alternate technique or method for p-doping for DBRs is necessary.
It can be seen that use of conventional p-type dopant materials do not meet the requirements for manufacturing or environmental considerations. Therefore, an alternative technique or method for p-type doping DBRs that will improve or equal performance levels, that will not impact environmental concerns, and that will simplify the method for fabrication would be highly desirable.